368 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



becomes promptly very long, and they remain a little broader than 

 long and triangular in shape. 



The first under arm plate is large, triangular, and as broad as long. 

 The two or three following plates are quadrangular with the proxi- 

 mal border narrow, the distal border very broadened and convex, 

 and the sides strongly excavated by the tentacle pores. Beyond the 

 plates become progressively elongated and pentagonal with an obtuse 

 proximal angle bounded by two short straight sides, two lateral 

 borders strongly excavated by the tentacle pores, and a very broad 

 and very convex distal side which is often resolved into two short 

 sides united by an obtuse angle. Beyond the disk these plates are 

 separated and the interval between them soon becomes very long. 



The side arm plates are much elongated. They carry only three 

 small papilliform spines which are very short and rather widely 

 separated from each other; one of the spines is situated toward the 

 middle of the distal border, and the two others occur respectively in 

 the vicinity of each angle, the dorsal and the ventral, of the plates. 



The tentacle pores of the three or four first pairs are very large. 

 Those of the first pair are widely open at their proximal end, which 

 is very close to the corresponding mouth slit ; they usually show on 

 either side four large scales, and sometimes five. The pores of the 

 second pair bear four scales outwardly, and three or four inwardly ; 

 the pores of the third pair have usually three scales on each border, 

 and those of the fourth pair two only ; then the number of the scales 

 progressively diminishes, and there remains only a single proximal 

 scale. 



The color of the specimen in alcohol is white. 



Affinities and distinctive features. — Amphiophiura spatulifera is 

 close to A. oediplax. which H. L. Clark described from specimens 

 from Japan, collected in between 322 and 448 meters (176 and 245 

 fathoms) of water. The type of this species was of small size, and 

 the diameter of the disk did not exceed 5 mm., the arms being 12 mm. 

 in length. The species from the Philippines differs from it in the 

 presence of small plates intercalated between the large plates of the 

 dorsal surface of the disk, which are especially numerous in speci- 

 men B, in the occurrence of two large interradial plates instead of 

 only one, in the form of the radial papillae, which are more elongated 

 and broadened in their outer portion so as to assume a spatulate 

 form, and in having the mouth shields broader, the tentacle scales 

 larger, the upper arm plates broadly triangular, and three small 

 arm spines instead of only one. 



Amphiophiura oediplax is itself near A. bullata (Wyville Thom- 

 son) and A. convexa (Lyman), but A. spatulifera differs consider- 

 ably from these species and can not in any way be confused with them. 



